The present invention relates to an apparatus in an infusor for a liquid food product, of the type which includes an autoclave with a conical bottom, the autoclave having an inlet for the product located in its upper region, the inlet being disposed to divide the incoming product into the autoclave into small droplets, the infusor further including an outlet for the product located in the lower region of the autoclave, as well as an inlet for steam.
Heat treating food products for increased shelf life is a well-known and often employed method. The food products may, for example, be various dairy products such as milk, cream or yoghurt. The heat treatment may be put into effect in a plurality of different ways, directly or indirectly. Indirect methods are, for instance, heating using various types of heat exchangers. There are two main groups of direct methods, injection or infusion with steam. By employing a direct method, an extremely rapid heating will be obtained, which is to be sought for today since, in order to improve the flavour qualities, for instance in milk, it is many times the intention to heat the product to elevated temperatures for a brief interval of time.
The present invention relates to an apparatus in which use is made of infusion heating. Infusion entails that a finely divided liquid is heated in a steam chamber. The principle of heating a liquid, for example a liquid food, by injecting the liquid into a chamber filled with steam is known from the later part of the nineteenth century.
In principle, the infusor consists of an autoclave with a conical bottom. In the upper region of the autoclave there is an inlet for the product which is to be heat treated and there is also a device for dividing the product into small droplets which then fall through the autoclave. At the bottom of the autoclave, the droplets gather and form a liquid accumulation and finally depart from the autoclave through an outlet in its lower region. The autoclave also has an inlet for steam which may be placed in its upper region or alternatively its lower region. Regardless of the siting of the steam inlet, the purpose of the hot steam is to heat up the product droplets on their way down through the autoclave.
All modern heat treatment of food products has for its purpose, on the one hand to heat the product to a certain predetermined temperature, and on the other hand to keep the product at this temperature for a given predetermined interval of time. In connection with the heating of the product in an infusor, use is normally made of a separate buffer cell or pipe, i.e. a pipe length in direct connection with the product outlet of the autoclave. When the product leaves the autoclave, it is at a temperature close to boiling point and the displacement proper entails a pressure drop which consequently causes the product to boil. This boiling may give rise to frothing which entails a volume reduction and reduced control over how the product may be kept at a given temperature for a given interval of time. In order to prevent the product from boiling before reaching the buffer cell or pipe, the requirements of the authorities in several countries have required that a so-called lobe rotor pump be placed between the autoclave and the buffer cell, with a view to imparting a pressure increase to the product and thereby preventing boiling. A relatively expensive pump such as a lobe rotor pump is necessary, since the product is at a temperature of approximately 140-150xc2x0 C.
The liquid accumulation of heated product which gathers in the conical bottom region of the autoclave causes great uncertainty in the calculation of the stay time of the product, since the relatively large volume involved makes it impossible to know how long the product stays here, and that all parts of the product have been treated for the same interval of time.
One object of the present invention is to realise a buffer cell in the infusor which gives a reliable and controlled stay time for the product. In that the buffer cell constitutes a part of the infusor, the need for an additional buffer cell is eliminated, as well as the need for any possible pump placed between the infusor and the buffer cell.
A further object of the present invention is to realise a buffer cell which may be simply regulated for different time intervals in respect of the stay time, in that the volume in the buffer cell may be varied.
These and other objects have been attained according to the present invention in that the apparatus of the type described by way of introduction has been given the characterizing features that the conical bottom of the autoclave is, for the greater part, filled by a conically shaped body and that the remaining space in the bottom of the autoclave constitutes a buffer cell.
Preferred embodiments of the present invention have further been given the characterizing features as set forth in the appended subclaims.